The present invention relates to portable computer systems which can receive external power from both AC and DC sources.
A typical power cord interfaces to a wall outlet at one end, and interfaces to a standard C-7 type AC connector at the other. The C-7 type AC connector is a widely used standard, and is illustrated in prior art FIG. 1A. This is a non-polarized connector which is normally located on the back of a portable computer. (The C-7 standard is defined by IEC section 320.) C-7 is not the only AC input connector, but is the smallest size which is rated for the 50 W or more power levels normally required for portable computer input.
By attaching the appropriate cord to the C-7 connector, the computer can be configured to operate in the U.S., Japan, U.K., France, Switzerland, Australia, India, etc. Of course, the power supply itself must be able to tolerate the different voltages and frequencies of mains power in these different locations, but power supplies which can accept any AC voltage from 100 volts up through 240 volts are widely available. Thus, the ability to use different power cords with a C-7 connector is very advantageous.
However, the standard definition of a type C-7 connector does not permit it to be used for DC power inputs. Thus, while the capability to accept both DC and AC power inputs is very useful, a separate connector is normally provided on the chassis of computers which can accept such input. (The DC inputs are typically 12 volts, for recharging in a car.) This requires not only separate circuitry, but also separate connectors and cords. Since space on the exterior surface of the chassis is at a premium, this is undesirable.